Polyurethane sword and method of manufacturing a polyurethane sword

ABSTRACT

Disclosed are polymeric swords and sparring instruments having improved mechanical properties and methods of making such swords and sparring instruments. In one embodiment, a polyurethane sword comprises a handle portion and a blade portion. In this embodiment, the polyurethane sword also comprises a flexible support member having a handle support portion and a blade support portion. In this embodiment, the polyurethane sword also comprises a polyurethane outer layer configured to encase the flexible support member from the handle support portion to the blade support portion. The handle portion comprises the handle support portion and the polyurethane outer layer encasing the handle support portion. Moreover, the blade portion comprises the blade support portion and the polyurethane outer layer encasing the blade support portion. In addition, the polyurethane outer layer may be composed of a machine perfused polyurethane mixture.

FIELD OF TECHNOLOGY

This disclosure relates generally to sparring instruments; and morespecifically, to a polyurethane sword and methods of manufacturing thepolyurethane sword.

BACKGROUND

The recent rise in the popularity of the fantasy genre in literaryworks, television, and films have brought about an attendant rise in thedemand for weaponry seen in such works. These types of weaponry areoften carried by fans of the genre to gatherings such as renaissancefaires (RenFaires), comic conventions (ComicCons), or costume play(CosPlay) events. The most popular form of such weaponry involve bladedinstruments such as longswords, broadswords, and sabres. Since publicvenues and events often ban steel or other metallic weaponry for publicsafety concerns, a popular alternative is to choose swords made ofpolymeric materials such as polyethylene (PE) or ethylene-vinyl acetate(EVA). However such swords often lack the look and feel of theirauthentic counterparts and are prone to tears, bends, or breaks.

Moreover, enthusiasts of combat sports such as fencing, wushu, and kendoare frequently in need of practice instruments that can mimic the weightand durability of real swords. While polymeric swords offer a safersurrogate to metallic instruments, most polymeric swords sold in themarket today bend or break upon repeated impact. In addition, wieldingsuch polymeric swords often leaves much to be desired as the weight ofthese swords tend to belie their decorative authenticity. Therefore,there is a need for a polymeric sword that can withstand the rigors ofactual sword play but still offer the look and feel of a metallic arm.

SUMMARY

Disclosed are polymeric swords and sparring instruments having improvedmechanical properties and methods of making such swords and sparringinstruments. In one aspect, a polyurethane sword comprises a handleportion and a blade portion. In this aspect, the polyurethane sword alsocomprises a flexible support member having a handle support portion anda blade support portion. In this aspect, the polyurethane sword alsocomprises a polyurethane outer layer configured to encase the flexiblesupport member from the handle support portion to the blade supportportion. In this aspect, the handle portion comprises the handle supportportion and the polyurethane outer layer encasing the handle supportportion. Moreover, the blade portion comprises the blade support portionand the polyurethane outer layer encasing the blade support portion. Inaddition, the polyurethane outer layer may be composed of a machineperfused polyurethane mixture.

In this aspect, the flexible support member may comprise a substantiallycylindrical hollow core extending from the handle support portion to theblade support portion. In this aspect, the diameter of the substantiallycylindrical hollow core may range from 0.5 mm to 1.5 mm. Moreover, thepolyurethane outer layer may expose a first aperture of thesubstantially cylindrical hollow core at a first end of the flexiblesupport member and expose a second aperture of the substantiallycylindrical hollow core at a second end of the flexible support member.In this aspect, the flexible support member may be composed of apolyester resin and fiberglass. Furthermore, the machine perfusedpolyurethane mixture may comprise 67% polyurethane polymers and 33%methylene diphenyl diisocyanate (MDI).

In another aspect, a method of making a polyurethane sword is disclosedcomprising the steps of: centering a flexible support member on either afirst half of a sword mold or on a second half of the sword mold;spraying a base coat paint on either the first half of the sword mold oron the second half of the sword mold; pouring a machine perfusedpolyurethane mixture in both halves of the sword mold and closing themold; heating the sword mold, and removing the polyurethane sword fromthe sword mold.

In this aspect, the method may further comprise the step of spraying awax-based release agent on the first half of the sword mold and on thesecond half of the sword mold before centering the flexible supportmember. In addition, the method may further comprise the step ofrotating the sword mold before heating the sword mold. Moreover, themethod may further comprise the step of hanging the sword mold from oneend for a period of time at room temperature after heating the swordmold. Finally, the method may further comprise the step of deburring thepolyurethane sword after removal from the sword mold. In this aspect,the step of heating the sword mold may comprise heading the sword moldat 45-55 degrees Celsius for a period of 10-15 minutes.

In yet another aspect, a sparring instrument is disclosed comprising ahandle portion and a distal portion. In this aspect, the sparringinstrument also comprises a support member having a handle supportportion and a distal support portion. In this aspect, a polyurethaneouter layer is configured to encase the support member from the handlesupport portion to the distal support portion. In this aspect, thehandle portion of the sparring instrument comprises the handle supportportion and the polyurethane outer layer encasing the handle supportportion of the support member. In addition, the distal portion of thesparring instrument comprises the distal support portion and thepolyurethane outer layer encasing the distal support portion of thesupport member. Furthermore, the polyurethane outer layer may becomposed of a machine perfused polyurethane mixture.

The methods and apparatus disclosed herein may be implemented in anymeans for achieving the various aspects. Other features will be apparentfrom the accompanying drawings and from the detailed description thatfollows.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments are illustrated by way of example and are notlimited to the figures of the accompanying drawings, in which, likereferences indicate similar elements.

FIG. 1 illustrates an exemplary polyurethane sword, according to one ormore embodiments.

FIG. 2 illustrates a close up view of the handle bottom of the exemplarypolyurethane sword of FIG. 1, according to one or more embodiments.

FIG. 3 illustrates a close up view of the blade tip of the exemplarypolyurethane sword of FIG. 1, according to one or more embodiments.

FIG. 4 illustrates a close up cross-sectional view of the blade portionof the exemplary polyurethane sword of FIG. 1, according to one or moreembodiments.

FIG. 5 is a schematic of an exemplary sword mold, according to one ormore embodiments.

FIG. 6 is a process flow diagram illustrating an exemplary method tomanufacture a polyurethane sword, according to one or more embodiments.

FIG. 7 is a process flow diagram illustrating an exemplary method tomanufacture a polyurethane sword, according to one or more embodiments.

FIGS. 8A and 8B are black-and-white images of exemplary polyurethaneswords, according to one or more embodiments.

FIG. 9A is a black-and-white image of a compression set test beingperformed on a portion of the polyurethane outer layer of an exemplarypolyurethane sword, according to one or more embodiments.

FIG. 9B is a black-and-white image of a flexural test being performed onan exemplary polyurethane sword.

FIG. 9C is a black-and-white image of an impact test being performed onthe blade portion of an exemplary polyurethane sword.

FIG. 9D is a black-and-white image of a transverse failure of a part ofthe blade portion of the exemplary polyurethane sword as a result of theimpact test shown in FIG. 9C.

FIG. 9E is a black-and-white image of a longitudinal failure of a partof the blade portion of the exemplary polyurethane sword as a result ofthe impact test shown in FIG. 9C.

Other features of the present embodiments will be apparent from theaccompanying drawings and from the detailed description that follows.

DETAILED DESCRIPTION

Disclosed are swords and sparring instruments having improved mechanicalproperties and methods of making such swords and sparring instruments.Although the present embodiments have been described with reference tospecific example embodiments, it will be evident that variousmodifications and changes may be made to these embodiments withoutdeparting from the broader spirit and scope of the various embodiments.Moreover, the components shown in the figures, their connections,couples, and relationships, and their functions, are meant to beexemplary only, and are not meant to limit the embodiments describedherein.

Reference is now made to FIG. 1 which illustrates an exemplarypolyurethane sword 100. In the embodiment shown in FIG. 1, thepolyurethane sword 100 comprises a blade portion 108 and a handleportion 110. In this embodiment, the polyurethane sword 100 alsocomprises a flexible support member 102 having a blade support portion114 and a handle support portion 116. In some embodiments, the flexiblesupport member 102 may be composed of a polyester resin and/orfiberglass. In these and other embodiments, the polyester resin may be athermosetting polyester resin. In other embodiments, the polyester resinmay be a vinyl ester resin. In all such embodiments, the flexiblesupport member 102 may be manufactured using an isophthalic procedure.

In one or more embodiments, the flexible support member 102 may comprisea substantially cylindrical hollow core extending from a first end 104of the flexible support member 102 to a second end 106 of the flexiblesupport member 102. In one embodiment, the first end 104 may be the endof the blade support portion 108 of the flexible support member 102.Moreover, the second end 106 may be the end of the handle supportportion 110 of the flexible support member 102. In some embodiments, thediameter of the substantially cylindrical hollow core may range from 0.5mm to 1.5 mm. In other embodiments, the diameter of the substantiallycylindrical hollow core may range from 1.5 mm to 3.0 mm. In additionalembodiments, the diameter of the substantially cylindrical hollow coremay range from 0.1 mm to 0.4 mm. In all such embodiments, the diameterof the substantially cylindrical hollow core may be sized in proportionto the cross-sectional dimensions of the polyurethane sword 100's swordblade. In some embodiments, the flexible support member 102 may be a rodcomprising a solid core.

In one or more embodiments, a polyurethane outer layer 112 may encasethe flexible support member 102 from the handle support portion 110 tothe blade support portion 108. In some embodiments, the polyurethaneouter layer 112 may be substantially shaped or molded as a sword handlewhen encasing the handle support portion 110 of the flexible supportmember 102 and substantially shaped as a sword blade when encasing theblade support portion 108 of the flexible support member 102. In thisand other embodiments, the handle portion 110 comprises the handlesupport portion 116 of the flexible support member 102 and thepolyurethane outer layer 112 encasing the handle support portion 116. Inthis and other embodiments, the blade portion 108 comprises the bladesupport portion 114 of the flexible support member 102 and thepolyurethane outer layer 112 encasing the blade support portion 114. Inall such embodiments, the polyurethane outer layer 112 may be composedof a machine perfused polyurethane mixture. As will be discussed in thesections that follow, a method of making the polyurethane sword 100 maycomprise the machine perfused polyurethane mixture being injected,poured, and/or extruded into a sword mold by a high-pressure pneumaticpolyurethane mixing apparatus.

In some embodiments, the polyurethane outer layer 112 may comprise aviscoelastic polyurethane. In other embodiments, the polyurethane outerlayer 112 may comprise a low-resistance polyurethane. In these and otherembodiments, the polyurethane outer layer 112 may comprise a low-densitypolyurethane. In one embodiment, the machine perfused polyurethanemixture may comprise a combination of polyurethane polymers andisocyanates. In one preferred embodiment, the isocyanate may bemethylene diphenyl diisocyanate (MDI). In this and other embodiments,the machine perfused polyurethane mixture may be composed of 67%polyurethane polymers and 33% methylene diphenyl diisocyanate (MDI). Insome embodiments, the polyurethane polymers may comprise any combinationof polymeric polyols (e.g., diols and triols). In one or moreembodiments, the polymeric polyols used may comprise polyethers orpolyesters. In these and other embodiments, the polyethers used maycomprise polyethylene glycol, polypropylene glycol, and/orpoly(tetramethylene ether) glycol. Alternatively, the polyesters usedmay comprise polybutadiene. In some embodiments, the machine perfusedpolyurethane mixture may comprise five (5) parts of water per onehundred (100) parts of polymeric polyols.

In one or more embodiments, the polyurethane outer layer 112 may exposea first aperture 300 (see FIG. 3) of the substantially cylindricalhollow core at the first end 104 of the flexible support member 102. Inaddition, the polyurethane outer layer 112 may expose a second aperture200 (see FIG. 2) of the substantially cylindrical hollow core at thesecond end 106 of the flexible support member 102. One benefit ofexposing such apertures is to improve the flexural properties of theflexible support member 102.

Reference is now made to FIG. 2, which illustrates a close up view ofthe bottom of the handle of the polyurethane sword 100, according to oneor more embodiments. As can be seen in FIG. 2, the polyurethane outerlayer 112 may expose the second aperture 200 of the substantiallycylindrical hollow core at the second end 106 of the flexible supportmember 102. In this and other embodiments, the polyurethane outer layer112 may encase the entire handle support portion 110 of the flexiblesupport member 102. In one embodiment, the polyurethane outer layer 112may be substantially shaped or molded as a handle when encasing thehandle support portion 110 of the flexible support member 102 without anadditional support member. In an alternative embodiment, an additionalsupport member may be coupled to the flexible support member 102 at thehandle support portion 110. In this and other embodiments, theadditional support member may be coupled to the flexible support member102 in a substantially perpendicular manner. In this alternativeembodiment, the polyurethane outer layer 112 may encase both theflexible support member 102 and the additional support member. In oneembodiment, the second aperture 200 may be shaped as a substantiallycircular aperture. In this and other embodiments, the diameter of thesecond aperture 106 may range from 0.5 mm to 1.5 mm. In alternativeembodiments, the diameter of the second aperture 106 may range from 1.5mm to 3.0 mm. In additional embodiments, the diameter of the secondaperture 106 may range from 0.1 mm to 0.4 mm.

Reference is now made to FIG. 3, which illustrates a close up view ofthe tip of the blade of the polyurethane sword 100, according to one ormore embodiments. As can be seen in FIG. 3, the polyurethane outer layer112 may expose a first aperture 300 of the substantially cylindricalhollow core at the first end 104 of the flexible support member 102. Inone or more embodiments, the first aperture 300 and the second aperture200 may form ends of the substantially cylindrical hollow core of theflexible support member 102. In one embodiment, the first aperture 300may be shaped as a substantially circular aperture. In this and otherembodiments, the diameter of the first aperture 300 may range from 0.5mm to 1.5 mm. In alternative embodiments, the diameter of the firstaperture 300 may range from 1.5 mm to 3.0 mm. In additional embodiments,the diameter of the first aperture 300 may range from 0.1 mm to 0.4 mm.

Reference is now made to FIG. 4, which illustrates a close upcross-sectional view of the blade portion 108 of the polyurethane sword100, according to one or more embodiments. In one preferred embodiment,the flexible support member 102 is positioned in a substantially centerposition of the polyurethane sword 100's sword blade. In this and otherembodiments, the polyurethane sword 100's sword blade is composedprimarily of the polyurethane outer layer 112 and the flexible supportmember 102. As can be seen from FIG. 4, the cross-section of theflexible support member 102 may be shaped as an annulus having a smallhollow core. In this embodiment, the flexible support member 102 isshaped as an open cylinder. Moreover, the thickness of the flexiblesupport member 102's cylinder wall surrounding its hollow core may rangefrom 2.0 mm to 3.0 mm. In other embodiments, the thickness of theflexible support member 102's cylinder wall surrounding its hollow coreranges from 3.0 mm to 4.0 mm. In additional embodiments, the thicknessof the flexible support member 102's cylinder wall surrounding itshollow core ranges from 4.0 mm to 5.0 mm. In these and otherembodiments, the thickness of the flexible support member 102's cylinderwall surrounding its hollow core may be sized in proportion to thelength of the flexible support member 102. In these cases, the greaterthe length of the flexible support member 102, the thicker the flexiblesupport member 102's cylinder wall surrounding its hollow core.

Reference is now made to FIG. 5, which is a schematic of an exemplarysword mold 500. As can be seen in FIG. 5, the sword mold 500 maycomprise a first half 502 and a second half 506. In some embodiments,one or more hinges may connect the first half 502 of the sword mold 500to the second half 506. Both the first half 502 and the second half 506of the sword mold 500 may be substantially shaped as a rectangle. In oneembodiment, the length of the rectangle may be equivalent to the lengthof the polyurethane sword 100 from the handle to the blade tip. As shownin FIG. 5, the first half 502 of the sword mold 500 may comprise a firstmold form 504 and the second half 506 of the sword mold 500 may comprisea second mold form 508. In one embodiment, the first mold form 504 maybe identical to the second mold form 508. In other embodiments, thefirst mold form 504 may be different from the second mold form 508depending on the surface ornamentation of the polyurethane sword 100.

In addition, the sword mold 500 may comprise a handle end 512 and ablade end 510. As seen in FIG. 5, one or more handlebars 514 may becoupled to the handle end 512 of the sword mold 500. In an embodimentnot shown in FIG. 5, the one or more handlebars 514 may be coupled tothe blade end 512 of the sword mold 500. In addition, a latch mechanism516 may be coupled to the first half 502 and/or the second half 506 ofthe sword mold 500 to secure the first half 502 of the sword mold 500 tothe second half 506. In this embodiment, the sword mold 500 operatessimilar to a suitcase where the first mold form 504 and the second moldform 508 act as the interior of the suitcase.

In some embodiments, the first mold form 504 and the second mold form508 may be configured to extend to the edges of the sword mold 500 atboth the handle end 512 and the blade end 510. By doing so, the swordmold 500 leaves an aperture or opening at the blade end 510 of the swordmold and an aperture or opening at the handle end 512 of the sword mold500. Such an arrangement also ensures that the first aperture 104 andthe second aperture 106 of the flexible support member 102 are exposedwhen the flexible support member 102 is placed in the center of eitherthe first mold form 504 or the second mold form 508.

In some embodiments, the sword mold 500 may be composed of a metallicmaterial (e.g., steel). In other embodiments, the sword mold 500 may becomposed of a ceramic material. In all such embodiments, the materialused to create the sword mold 500 must be capable of withstanding heatof at least 45 degrees Celsius.

Reference is now made to FIG. 6, which is a process flow diagramillustrating an exemplary method to manufacture a polyurethane sword. Inone embodiment, the exemplary method may be used to manufacture thepolyurethane sword 100 of FIG. 1. In this embodiment, step 600 involvescentering the flexible support member 102 on either the first half 502(in the first mold form 504) or on the second half 506 (in the secondmold form 508) of the sword mold 500. In one embodiment, the length ofthe flexible support member 102 may be greater than the length of thesword mold 500 and one or both ends of the flexible support member 102may protrude from the apertures at the blade end 510 and the handle end512 of the sword mold 500. In this embodiment, the ends of the flexiblesupport member 102 that protrude from the apertures may later be cut sothat the length of the flexible support member 102 may be substantiallyequal to the length of the polyurethane sword 100 once the polyurethanesword 100 has been removed from the sword mold 500. In otherembodiments, the length of the flexible support member 102 may besubstantially equal to the length of the sword mold 500.

Additionally, step 602 may involve spraying a base coat paint on thefirst half 502 (on the first mold form 504) and/or the second half 506(on the second mold form 508) of the sword mold 500. In one embodiment,the base coat paint may be an acrylic paint. Step 604 may involvepouring, injecting, and/or extruding a machine perfused polyurethanemixture (for example, the machine perfused polyurethane mixturediscussed in the preceding sections) into the first half 502 (in thefirst mold form 504) and the second half 506 (in the second mold form508) of the sword mold 500. In one embodiment, the machine perfusedpolyurethane mixture may be injected, poured, and/or extruded into thesword mold 500 by a pneumatic polyurethane mixing apparatus at highpressure. In addition, the step involves closing the sword mold 500 bylatching or clasping the first half 502 of the sword mold 500 to thesecond half 506 of the sword mold 500. In one embodiment, the first half502 of the sword mold 500 may be latched or clasped to the second half506 of the sword mold using the latch mechanism 516. Moreover, step 606involves heating the sword mold 500 comprising the machine perfusedpolyurethane mixture in a heating apparatus. In one embodiment, theheating apparatus may be a curing oven. In another embodiment, theheating apparatus may be a baking oven. In yet another embodiment, theheating apparatus may be a batch oven.

In these and other embodiments, the step of heating the sword mold 500may involve heating the sword mold 500 at a heating temperature ofbetween 45 to 55 degrees Celsius for 10 to 15 minutes. In an alternativeembodiment, the heating step may be performed at a heating temperatureof between 40 to 45 degrees for 15 to 20 minutes. In yet anotherembodiment, the heating step may be performed at a heating temperatureof between 55 to 65 degrees Celsius for 5 to 10 minutes. Once the heatedsword mold 500 has been removed from the heating apparatus and the swordmold 500 has been allowed to rest at room temperature, the sword mold500 can be opened and the polyurethane sword can be removed from thesword mold 500 in step 608.

Reference is now made to FIG. 7, which is a process flow diagramillustrating another exemplary method to manufacture a polyurethanesword. In one embodiment, the method may be used to manufacture thepolyurethane sword 100 of FIG. 1. In this embodiment, step 700 involvesspraying a wax-based release agent on the first half 502 (on the firstmold form 504) and/or the second half 506 (on the second mold form 508)of the sword mold 500. The wax-based release agent may aid in theremoval of the polyurethane sword from the sword mold 500 after the moldhas been heated. Step 702 involves centering the flexible support member102 in either the first half 502 (in the first mold form 504) or in thesecond half 506 (in the second mold form 508) of the sword mold 500.

As discussed previously, the length of the flexible support member 102may initially be greater than the length of the sword mold 500 and oneor both ends of the flexible support member 102 may protrude from theapertures at the blade end 510 and the handle end 512 of the sword mold500. In this embodiment, the ends of the flexible support member 102that protrude from the apertures may later be cut so that the length ofthe flexible support member 102 is substantially equal to the length ofthe polyurethane sword 100 once the polyurethane sword 100 has beenremoved from the sword mold 500. In other embodiments, the length of theflexible support member 102 may initially be substantially equal to thelength of the sword mold 500.

Additionally, step 704 may involve spraying a base coat paint on thefirst half 502 (on the first mold form 504) and/or the second half 506(on the second mold form 508) of the sword mold 500. In one embodiment,the base coat paint may be an acrylic paint. Step 706 may involvepouring, injecting, and/or extruding a machine perfused polyurethanemixture (for example, the machine perfused polyurethane mixturediscussed in the preceding sections) into the first half 502 (in thefirst mold form 504) and the second half 506 (in the second mold form508) of the sword mold 500. In one embodiment, the machine perfusedpolyurethane mixture may be injected, poured, and/or extruded into thesword mold 500 by a pneumatic polyurethane mixing apparatus at highpressure. In addition, the step involves closing the sword mold 500 bylatching or clasping the first half 502 of the sword mold 500 to thesecond half 506 of the sword mold 500. In one embodiment, the first half502 of the sword mold 500 may be latched or clasped to the second half506 of the sword mold using the latch mechanism 516.

Step 708 involves rotating the closed sword mold 500 around itslongitudinal center of axis. This rotation step may be needed so thatthe machine perfused polyurethane mixture permeates the entirety of theinterior of the sword mold 500. In addition, step 710 involves heatingthe sword mold 500 comprising the machine perfused polyurethane mixturein a heating apparatus. In one embodiment, the heating apparatus may bea curing oven. In another embodiment, the heating apparatus may be abaking oven. In yet another embodiment, the heating apparatus may be abatch oven.

In these and other embodiments, the step of heating the sword mold 500may involve heating the sword mold 500 at a heating temperature ofbetween 45 to 55 degrees Celsius for 10 to 15 minutes. In an alternativeembodiment, the heating step may be performed at a heating temperatureof between 40 to 45 degrees for 15 to 20 minutes. In yet anotherembodiment, the heating step may be performed at a heating temperatureof between 55 to 65 degrees Celsius for 5 to 10 minutes.

Once the heated sword mold 500 has been removed from the heatingapparatus, step 712 involves hanging the sword mold 500 by its one ormore handlebars 514 for a period of time at room temperature. In oneembodiment, the sword mold 500 may be hung from its handle end 512 usingthe one or more handlebars 514. In another embodiment, the sword mold500 may be hung from its blade end 510 using the one or more handlebars514. In some embodiments, the sword mold 500 may be hung at roomtemperature for a period of 45 to 60 minutes. In other embodiments, thesword mold 500 may be hung at room temperature in excess of 60 minutes.Once the sword mold 500 has been hung at room temperature for a periodof time, the sword mold 500 can be opened and the polyurethane sword 100can be removed from the sword mold 500 in step 714. Furthermore, themethod may also comprise the step of deburring the polyurethane sword100 after removing it from the sword mold 500. In some embodiments, thedeburring step can be performed by a deburring machine. In otherembodiments, the deburring step can be performed manually using adeburring tool.

Reference is now made to FIGS. 8A and 8B, which are black-and-whiteimages of exemplary polyurethane swords manufactured using theaforementioned methods. As can be seen in both images, the visualappearance of the polyurethane swords exhibit a likeness to metallicswords unlike traditional toy-type swords. Also, as seen in the images,the handle portion of the polyurethane sword may be decorated furtherwith additional coats of paint and surface ornamentation. In the exampleembodiment shown in FIGS. 8A and 8B, the handles of the polyurethaneswords may be meticulously painted to mimic swords of a certain era orgeographic region.

Reference is now made to FIG. 9A, which is a black-and-white image of acompression set test being performed on a portion of the polyurethaneouter layer 112 of an exemplary polyurethane sword (for example, thepolyurethane sword 100) manufactured according to the methods describedin the preceding sections. In the field of polymers, compression settesting is used to determine a polymer material's ability to retainelastic properties after prolonged compressive stresses. A series ofcompression set tests were performed in accordance with American Societyfor Testing and Materials (ASTM) D395-03 (2008), Standard Test Methodsfor Rubber Property—Compression Set, Method B. A flat section of thepolyurethane outer layer 112 of the polyurethane sword 100 was used asthe sample material. The sample height was measured with a Mitutoyo® 6inch digital caliper. The sample was then compressed to 25% of itsoriginal thickness (also referred to as: 75% compressive deformation)for a period of 24 hours at 23 degrees Celsius and 50% relative humidity(as measured by an Omega® Hygrometer). After 24 hours, the sample wasthen removed and allowed to rebound for 30 minutes. The final thicknessof the sample was measured and the compression set calculated. The testwas then repeated on additional polyurethane swords manufacturedaccording to the methods described in the preceding sections. Theresults of such tests revealed that the polyurethane outer layer 112 ofsuch swords exhibited a compression set of between 2.9% to 5.8% whenmeasured at a 75% compressive deformation level. For example, in onesuch test, the initial thickness of the polyurethane outer layer 112sample was approximately 0.445 inches. After being compressed toapproximately 0.342 inches for 24 hours, the sample rebounded to 0.440inches after 30 minutes, exhibiting a compression set of 4.85%.

Reference is now made to FIG. 9B, which is a black-and-white image of aflexural test being performed on a portion of the blade portion 108 ofan exemplary polyurethane sword (for example, the polyurethane sword100) manufactured according to the methods described in the precedingsections. The flexural properties of the polyurethane sword wasdetermined in accordance with ASTM D790-10, Standard Test Methods ofUnreinforced and Reinforced Plastics and Insulating Materials. A TiniusOlsen® H50K-S Universal Load Tester was utilized to test the entiresword (including both the blade portion 108 and the handle portion 110)using a 3-point loading orientation. An 18 inch span was chosen in orderto accommodate a significant portion of the blade portion 108. Theflexural load (a Tinius Olsen® 1,000 lb Load Cell) was applied at themidpoint of the blade portion 108 at a rate of 2 inches/minute. Multiplepolyurethane swords were tested and the load and deflection distanceswere recorded at the time of failure. All tests were performed at 23degrees Celsius and 50% relative humidity was measured by an Omega®Hygrometer. The results of such tests revealed that the polyurethanesword is configured to withstand a maximum flexural load of between 300Newtons to 360 Newtons of force with an average maximum deflectiondistance of approximately 12 cm.

Reference is now made to FIG. 9C, which is a black-and-white image of animpact test being performed on a portion of the blade portion 108 of anexemplary polyurethane sword (for example, the polyurethane sword 100)manufactured according to the methods described in the precedingsections. A series of impact tests were performed in accordance withASTM D6110-10, Standard Test Methods for Determining the Charpy ImpactResistance of Notched Specimens of Plastics. A 5 inch sample segment(including both the polyurethane outer layer 112 and the flexiblesupport member 102) was cut from the blade portion 108 of thepolyurethane sword and tested using a Tinius Olsen® Charpy Impact Testerutilizing a 4 inch span. Tests were performed on multiple polyurethaneswords and the impact energies and failure modes of such swords wererecorded.

As can be seen in FIGS. 9D and 9E, failures occurred as eitherlongitudinal failures of the flexible support member 102 or transversefailures of the polyurethane outer layer 112 and/or the flexible supportmember 102. FIG. 9D is a black-and-white image depicting a transversefailure of the 5 inch sample segment as a result of the impact test.FIG. 9E is a black-and-white image depicting a longitudinal failure of asegment of the flexible support member 102 as a result of the impacttest. The results of such tests revealed that the blade portion 108 ofthe polyurethane sword is configured to withstand an impact of between19.6 Joules to 22.5 Joules of energy before the blade portion 108experiences either a transverse failure or a longitudinal failure. Thesetest results reveal that the polyurethane swords manufactured using themethods disclosed herein comprises certain key mechanical propertiessuperior to those exhibited by other toy-type swords.

Also disclosed is a sparring instrument (a club, a bat, a staff, etc.)comprising a support member (similar to the flexible support member 102)having a handle portion and a distal portion. In addition, the sparringinstrument's support member may also comprise a handle support portionand a distal support portion. In one or more embodiments, the sparringinstrument may share all of the attributes of the polyurethane sword 100of FIG. 1 except the distal portion of the sparring instrument is notshaped as a blade. In this embodiment, a polyurethane outer layer(similar to the polyurethane outer layer 112) may be configured toencase the support member from the handle support portion to the distalsupport portion. In this and other embodiments, the handle portion ofthe sparring instrument comprises the handle support portion and thepolyurethane outer layer encasing the handle support portion. Moreover,the distal portion of the sparring instruments comprises the distalsupport portion and the polyurethane outer layer encasing the distalsupport portion. Similar to the polyurethane sword 100, the polyurethaneouter layer encasing the support member may be composed of a machineperfused polyurethane mixture. In one or more embodiments, the machineperfused polyurethane mixture comprises 67% polyurethane polymers and33% MDI.

In these and other embodiments, the support member may comprise asubstantially cylindrical hollow core extending from the handle supportportion to the distal support portion. Moreover, the polyurethane outerlayer may expose a first aperture of the substantially cylindricalhollow core at a first end (similar to the first end 104) of the supportmember and a second aperture of the substantially cylindrical hollowcore at a second end (similar to the second end 106) of the supportmember. Moreover, the support member may be composed of a polyesterresin and fiberglass.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the claimed embodiments. In addition, the logicflows depicted in the figures do not require the particular order shown,or sequential order, to achieve desirable results. In addition, othersteps may be provided, or steps may be eliminated, from the describedflows, and other components may be added to, or removed from, thedescribed systems. Accordingly, other embodiments are within the scopeof the following claims.

The structures and modules in the figures may be shown as distinct andcommunicating with only a few specific structures and not others. Thestructures may be merged with each other, may perform overlappingfunctions, and may communicate with other structures not shown to beconnected in the figures. Accordingly, the specification and/or drawingsmay be regarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. A polyurethane sword, comprising: a handleportion and a blade portion; a flexible support member comprising ahandle support portion and a blade support portion; and a polyurethaneouter layer configured to encase the flexible support member from thehandle support portion to the blade support portion, wherein the handleportion comprises the handle support portion and the polyurethane outerlayer encasing the handle support portion, wherein the blade portioncomprises the blade support portion and the polyurethane outer layerencasing the blade support portion, wherein the polyurethane outer layeris composed of a machine perfused polyurethane mixture, wherein theflexible support member comprises a substantially cylindrical hollowcore extending from the handle support portion to the blade supportportion, and wherein the polyurethane outer layer exposes a firstaperture of the substantially cylindrical hollow core at a first end ofthe flexible support member and exposes a second aperture of thesubstantially cylindrical hollow core at a second end of the flexiblesupport member.
 2. The polyurethane sword of claim 1, wherein thediameter of the substantially cylindrical hollow core ranges from 0.5 mmto 1.5 mm.
 3. The polyurethane sword of claim 1, wherein the flexiblesupport member is composed of a polyester resin and fiberglass.
 4. Thepolyurethane sword of claim 1, wherein the machine perfused polyurethanemixture comprises 67% polyurethane polymers and 33% methylene diphenyldiisocyanate (MDI).
 5. The polyurethane sword of claim 1, wherein thepolyurethane outer layer exhibits a compression set of between 2.9% to5.8% when measured at a 75% compressive deformation level.
 6. Thepolyurethane sword of claim 1, wherein the polyurethane sword isconfigured to withstand a maximum flexural load of between 300 Newtonsto 360 Newtons when the maximum flexural load is applied at the midpointof the blade portion.
 7. The polyurethane sword of claim 1, wherein theblade portion is configured to withstand an impact of between 19.6Joules to 22.5 Joules before the blade portion experiences either atransverse failure or a longitudinal failure.
 8. A sparring instrument,comprising: a handle portion and a distal portion; a support membercomprising a handle support portion and a distal support portion; and apolyurethane outer layer configured to encase the support member fromthe handle support portion to the distal support portion, wherein thehandle portion comprises the handle support portion and the polyurethaneouter layer encasing the handle support portion, wherein the distalportion comprises the distal support portion and the polyurethane outerlayer encasing the distal support portion, wherein the polyurethaneouter layer is composed of a machine perfused polyurethane mixture,wherein the support member comprises a substantially cylindrical hollowcore extending from the handle support portion to the distal supportportion, and wherein the polyurethane outer layer exposes a firstaperture of the substantially cylindrical hollow core at a first end ofthe support member and a second aperture of the substantiallycylindrical hollow core at a second end of the support member.
 9. Thesparring instrument of claim 8, wherein the machine perfusedpolyurethane mixture comprises 67% polyurethane polymers and 33%methylene diphenyl diisocyanate (MDI).
 10. The sparring instrument ofclaim 8, wherein the sparring instrument is configured to withstand amaximum flexural load of between 300 Newtons to 360 Newtons when themaximum flexural load is applied at the midpoint of the distal portion.